The API currently has a window.open_file() method, but if you pass it the name of an already-opened file, it simply shows that view rather than opening a new view into the file. There should be a way to indicate that you actually want a new view into the file -- perhaps another flag that can be passed to the API.

Since the "New View into File" command exists in the menu, this functionality probably exists already in ST2, and simply isn't documented. If that is the case, please document it!